A hybrid type liquid crystal-display device is disclosed, for example, in the Japanese Unexamined Patent Publication No. 11-52366 and the Japanese Unexamined Patent Publication No. 11-183892. A hybrid type liquid crystal display device performs reflection type display by using an outside light by reflecting the outside light irradiating from the front surface side on a reflection layer on the back surface side when a sufficiently bright outside light (natural light and room lighting, etc.) can be obtained, while when sufficient outside light cannot be obtained, it performs transmission type display by using a light of a backlight arranged on the back surface side of the liquid crystal display device.
FIGS. 1A and 1B are schematic views of an example of a conventional hybrid type liquid crystal display device. FIG. 1A shows the configuration of a section of one pixel.
As shown in the figures, the hybrid type liquid crystal display device comprises a pair of a first substrate 1 and a second substrate 2 arranged facing to each other at the front and back. On the inner surface side of the first substrate 1 is formed a transparent common electrode 3, and on the inner surface side of the second substrate 2 is formed a pixel electrode 4. A pixel is formed at a part where the common electrode 3 formed on the first substrate 1 and respective pixel electrodes 4 formed on the second substrate 2 face to each other. By being matched with the pixel, a color filter CF is provided on the first (front side) substrate 1.
Below, the first substrate 1 provided with the color filter CF will be referred to as a CF substrate in some cases in the present specification.
A liquid crystal layer 5 as an electric optical layer is held between the pair of the first and second substrates 1 and 2 at the front and back. The liquid crystal layer 5 blocks/transmits an incident light for each pixel in response to a voltage applied between the electrodes 3 and 4.
The second (back side) substrate 2 is provided with a reflection layer 6. The reflection layer 6 has an opening for every pixel and flatly divides each pixel to a transmission portion T in the opening and a reflection portion R outside the opening. In the present example, the reflection layer 6 is made of a metal film formed on a relief shape surface of the substrate 2 and composes a part of the pixel electrode 4 explained above. Also, the transmission portion T is formed a transparent conductive film, such as ITO, and the opening explained above is formed and composes a part of the pixel electrode 4.
As is clear from the above explanation, the pixel electrode 4 formed on the second substrate 2 has the hybrid configuration of the metal film provided to the reflection portion R and the transparent conductive film provided on the transmission portion T. Such a pixel electrode 4 is driven for every pixel by a switching element, for example, driven by a thin film transistor (TFT).
The second substrate 2 being formed the TFT for driving pixels will be referred to as a TFT substrate in some cases in the present specification below.
The color filter CF is separately configured for a reflection region CFR corresponding to the reflection region R and a transmission region CFT corresponding to the transmission region T by using different materials. As shown in the figure, a light transmits the color filter CF twice in the reflection region CFR. On the other hand, a light transmits the color filter CF only once in the transmission region CFT.
Therefore, in order not to cause much difference in color tone between the reflection portion R and the transmission portion T, a coloring concentration of the reflection region CFR is made lower than that of the transmission region CFT in advance. For this reason, even a part of a color filter CF colored to be an identical color in an identical pixel was conventionally produced by separate processes by using different materials in the reflection region CFR and the transmission region CFT.
FIG. 1B schematically illustrates a plane shape of a liquid crystal display device shown in FIG. 1A. As shown in the figure, respective pixels PXL are separated in lattice by a black mask BM. Each pixel PXL is flatly divided to a transmission portion T at the center and a reflection portion R around it and has a so-called hybrid configuration. The color filter is patterned so as to approximately correspond to the pixels marked off by the black mask BM. Typically, pixel regions of the color filter corresponding to respective pixels PXL are colored to be three primary colors, red, green and blue.
A hybrid type liquid crystal display device aims to always realize an easy-to-watch display under any circumstances. Thus, it becomes a reflection type display for displaying a screen by using a reflection light in the same way as a printed matter in a bright circumstance, while in a dark circumstance, it becomes a transmission type display by using a backlight. To realize a color display by such a hybrid type display, it is necessary to form a color filter adjusted to the transmission type and a color filter adjusted to the reflection type on the CF substrate side. Conventionally, a method of forming a color filter separately through a production process of a transmission type CF and a production process of a reflection type CF was general.
However, this method requires a longer production process and more materials and kinds to be used. Therefore, there is a disadvantage that a color filter used in a hybrid type display becomes double in production costs comparing with a color filter used in a normal transmission type display.
Also, when forming both of the transmission type color filter and the reflection type color filter in one pixel, there is a disadvantage that the transmittance or reflectance declines when an alignment error arises between the two.